CA1071944A - Sealing layer for protective ceramic coatings on strip moulds of continuous strip casting machines - Google Patents
Sealing layer for protective ceramic coatings on strip moulds of continuous strip casting machinesInfo
- Publication number
- CA1071944A CA1071944A CA222,547A CA222547A CA1071944A CA 1071944 A CA1071944 A CA 1071944A CA 222547 A CA222547 A CA 222547A CA 1071944 A CA1071944 A CA 1071944A
- Authority
- CA
- Canada
- Prior art keywords
- sealing layer
- coating
- strip
- ceramic
- moulds
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Coating By Spraying Or Casting (AREA)
Abstract
ABSTRACT
A sealing layer for a porous coating of ceramic materials, which is applied in particular to strip moulds of a continuous casting unit. The sealing layer consists of an organic resin or at least of one fine partic-ulate inorganic substance or of a colloidal lubricating agent.
A sealing layer for a porous coating of ceramic materials, which is applied in particular to strip moulds of a continuous casting unit. The sealing layer consists of an organic resin or at least of one fine partic-ulate inorganic substance or of a colloidal lubricating agent.
Description
1 0 ~ i 9 4 4 The invention concerns a coating of thermall~ insulating material for ', 3 k~ a continuous strip casting machine such as, for example, the Hazelett strip caster.
With this continuous casting process liquid metals e.g. aluminum, copper, zinc, steel and alloys of these metals are cast in strip form. Two moving endless strips which are usually made of steel, are guided over supporting rolls and deflection rolls in such a way that they form a para-llel gap into which the liquid metal is cast. The heat of solidification is conducted away by the steel strips which are cooled with water on the other side.
In order to control the rate of removal of the heat, the steel strips are provided with a coating. This coating prevents the steel strips from warping due to overheating when they are in contact with the liquid metal.
At the same time, heat transfer during the solidification is controlled in such a way that, in particular in the production of aluminum strips, metall-urgically sound strips of cast metal are produced.
The coatings on the steel strips must simultaneously satisfy a series of conditions difficult to fulfil. The coatings must have heat resistance, resistance to high temperature and thermal shock, good adhesion to the steel strip, the ability to be uniformly deposited, long life wear resistance and flexibility in order to avoid cracks forming when the strip is in service.
Some of these requirements are met by a number of known coatings. For ex-ample organic resins such as polyvinylpyrrolidon (PVP) or silicones are sometimes used, mixed with suitable lubricating and insulating materials.
Many of the known coatings have however a pronounced disadvantage in that they abrade the solidifying strip. Furthermore, since the organic resins are heat resistant only up to temperatures far below the temperature of the liquid melt, their lifetime is limited. They are therefore often prevented from coming into direct contact with the liquid metal by means of finely dispersed materials. This increases the lifetime but adds the d:isadvantage f ~w~
:
, ; . . . . .. . .: . - .: , ,. .. : . . . :
~ 94 of transfer of the finely dispersed materials to the cast strip.
In order to avoid these difficulties a coati-ng of ceramic materials, deposited by means of thermal spraying, in particular plasma spraying, has been developed. This ceramic coating has the decisivle advantage of having resistance to high temperature and also complete freedom from wear. Its lifetime is very long and therefore, in contrast to the known coatings it is considered a permanent coating.
This coating has a certain porosity which can lead to the coating taking up moisture from the surrounding atmosphere. The atmosphere can have a high moisture content as large quantities of water circulate around the sides of the caster. These pores, together with a certain roughness in the surface of the coating lead to the liquid metal that flows between the steel strips wetting the surface of the coating non-~miformly. rrhis Ls particularly so when the metal is alumLnum. The non-unlEorm wetting produces surfaced Elaws on the cast strip generally known as segregation scars.
This invention relates to a method of use of a sealing layer for a porous coating of ceramic materials, said coating being applied to strip molds in a contlnuous casting operation, wherein said sealing layer consists of an organic resin or at least of one fine particulate inorganic substance or of a colloidal lubricating agent, wherein saLd sealing layer precludes said coating from taking up moisture and thereby forming water vapor on contact with liquid metal.
The invention seeks to improve the above described wetting behaviour by sealing the pores or by providing the coating with another layer of material.
Thus, the present invention provides a sealing layer for a porous coating of ceramic materials, which is applied to strip moulds of a continuous casting unit, which sealing layer consists of an organic resin or at least of one fine particulate inorganic substance or of a colloidal lubricating agent.
By sealing the pores with an organic resin such as polyphenylene sulphide (PPS), polybenzimidicarbazole (PBI), polyvinylpyrrolidone (PVP), poly-imides, silicone resins or at least one fine particulate substance such as graphite, zirconium silicate, hexagonal boron nitride, talc, ceramically bonded 10~1944 aluminum, or by the applicatîon of a thin protective layer of, for example, Fiberfrax QF/50 of carborundum, or by working in a lubricant such as graphite, magnesium hydroxide or electrophoretically applied silicon dioxide, the uptake of moisture is prevented and the formation of water vapour on contact with the liquid metal avoided. At the same time the wetting nature of the liquid metal on the coating is changed so that a smooth clean surface is obtained on the cast strip.
The relationships between the pores in the coating, humidity, sealing agents and wetting or surface finish of the cast strip have not yet been .' ' ' '. . '. ' * Trade mark :
' -2a- ~
,- : . . .: , 10719~
completely explained. It was found in trials however that the ~aterials used prevent segregation from forming and improve the surface of the cast strip.
The sealing agents adhere in the pores of a ceramic coating extremely well and lead, even after partially burning away, to a degree of wear in contacting the strip, which does not impair the quality of the product. Use-fully the thickness of the sealing layer (with the e~ception of Fiberfrax~
should not exceed the average depth of irregularity which makes up the rough-ness in the ceramic coating i.e. a depth of 1~20 microns. The sealing layer should definitely not constitute a complete covering layer over the ceramic coating.
The invention will be further described with reference to the accomp-anying drawings in which:
Figure 1 is a diagram of the continuou9 casting proces9, and Figure 2 illustrates a strip mould having a sealing layer according to the invention.
In Figure 1 two moving endless steel strips 1 are guided over support- -ing and deflecting roller 2 to form a parallel-sided space 3. Liquid metal 4 is flowed into the space 3 where it solidifies. To assist solidification the strips 1 are cooled with water from jets 5.
Figure 2 shows an enlarged section of a strip mould 6, which has a cerc~mic coating 7 on it, in particular a coating depo9ited by plasma 9praying, the pores 8 of which have been sealed or blocked up, whilst the closed pores 9 or those away from the surface are not sealed.
With this continuous casting process liquid metals e.g. aluminum, copper, zinc, steel and alloys of these metals are cast in strip form. Two moving endless strips which are usually made of steel, are guided over supporting rolls and deflection rolls in such a way that they form a para-llel gap into which the liquid metal is cast. The heat of solidification is conducted away by the steel strips which are cooled with water on the other side.
In order to control the rate of removal of the heat, the steel strips are provided with a coating. This coating prevents the steel strips from warping due to overheating when they are in contact with the liquid metal.
At the same time, heat transfer during the solidification is controlled in such a way that, in particular in the production of aluminum strips, metall-urgically sound strips of cast metal are produced.
The coatings on the steel strips must simultaneously satisfy a series of conditions difficult to fulfil. The coatings must have heat resistance, resistance to high temperature and thermal shock, good adhesion to the steel strip, the ability to be uniformly deposited, long life wear resistance and flexibility in order to avoid cracks forming when the strip is in service.
Some of these requirements are met by a number of known coatings. For ex-ample organic resins such as polyvinylpyrrolidon (PVP) or silicones are sometimes used, mixed with suitable lubricating and insulating materials.
Many of the known coatings have however a pronounced disadvantage in that they abrade the solidifying strip. Furthermore, since the organic resins are heat resistant only up to temperatures far below the temperature of the liquid melt, their lifetime is limited. They are therefore often prevented from coming into direct contact with the liquid metal by means of finely dispersed materials. This increases the lifetime but adds the d:isadvantage f ~w~
:
, ; . . . . .. . .: . - .: , ,. .. : . . . :
~ 94 of transfer of the finely dispersed materials to the cast strip.
In order to avoid these difficulties a coati-ng of ceramic materials, deposited by means of thermal spraying, in particular plasma spraying, has been developed. This ceramic coating has the decisivle advantage of having resistance to high temperature and also complete freedom from wear. Its lifetime is very long and therefore, in contrast to the known coatings it is considered a permanent coating.
This coating has a certain porosity which can lead to the coating taking up moisture from the surrounding atmosphere. The atmosphere can have a high moisture content as large quantities of water circulate around the sides of the caster. These pores, together with a certain roughness in the surface of the coating lead to the liquid metal that flows between the steel strips wetting the surface of the coating non-~miformly. rrhis Ls particularly so when the metal is alumLnum. The non-unlEorm wetting produces surfaced Elaws on the cast strip generally known as segregation scars.
This invention relates to a method of use of a sealing layer for a porous coating of ceramic materials, said coating being applied to strip molds in a contlnuous casting operation, wherein said sealing layer consists of an organic resin or at least of one fine particulate inorganic substance or of a colloidal lubricating agent, wherein saLd sealing layer precludes said coating from taking up moisture and thereby forming water vapor on contact with liquid metal.
The invention seeks to improve the above described wetting behaviour by sealing the pores or by providing the coating with another layer of material.
Thus, the present invention provides a sealing layer for a porous coating of ceramic materials, which is applied to strip moulds of a continuous casting unit, which sealing layer consists of an organic resin or at least of one fine particulate inorganic substance or of a colloidal lubricating agent.
By sealing the pores with an organic resin such as polyphenylene sulphide (PPS), polybenzimidicarbazole (PBI), polyvinylpyrrolidone (PVP), poly-imides, silicone resins or at least one fine particulate substance such as graphite, zirconium silicate, hexagonal boron nitride, talc, ceramically bonded 10~1944 aluminum, or by the applicatîon of a thin protective layer of, for example, Fiberfrax QF/50 of carborundum, or by working in a lubricant such as graphite, magnesium hydroxide or electrophoretically applied silicon dioxide, the uptake of moisture is prevented and the formation of water vapour on contact with the liquid metal avoided. At the same time the wetting nature of the liquid metal on the coating is changed so that a smooth clean surface is obtained on the cast strip.
The relationships between the pores in the coating, humidity, sealing agents and wetting or surface finish of the cast strip have not yet been .' ' ' '. . '. ' * Trade mark :
' -2a- ~
,- : . . .: , 10719~
completely explained. It was found in trials however that the ~aterials used prevent segregation from forming and improve the surface of the cast strip.
The sealing agents adhere in the pores of a ceramic coating extremely well and lead, even after partially burning away, to a degree of wear in contacting the strip, which does not impair the quality of the product. Use-fully the thickness of the sealing layer (with the e~ception of Fiberfrax~
should not exceed the average depth of irregularity which makes up the rough-ness in the ceramic coating i.e. a depth of 1~20 microns. The sealing layer should definitely not constitute a complete covering layer over the ceramic coating.
The invention will be further described with reference to the accomp-anying drawings in which:
Figure 1 is a diagram of the continuou9 casting proces9, and Figure 2 illustrates a strip mould having a sealing layer according to the invention.
In Figure 1 two moving endless steel strips 1 are guided over support- -ing and deflecting roller 2 to form a parallel-sided space 3. Liquid metal 4 is flowed into the space 3 where it solidifies. To assist solidification the strips 1 are cooled with water from jets 5.
Figure 2 shows an enlarged section of a strip mould 6, which has a cerc~mic coating 7 on it, in particular a coating depo9ited by plasma 9praying, the pores 8 of which have been sealed or blocked up, whilst the closed pores 9 or those away from the surface are not sealed.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of use of a sealing layer for a porous coating of ceramic materials, said coating being applied to strip molds in a continuous casting operation, wherein said sealing layer consists of an organic resin or at least of one fine particulate inorganic substance or of a colloidal lubri-cating agent, wherein said sealing layer precludes said coating from taking up moisture and thereby forming water vapor on contact with liquid metal.
2. A method according to claim 1 in which the organic resins are polyphenylene sulphide, polybenzimidicarbazole, polyvinylpyrrolidone, poly-imides or silicone resins.
3. A method according to claim 1 in which the inorganic substances are selected from the group consisting of graphite, zirconium-silicate, hex-agonal boron nitride, talc, ceramic bonded aluminum and mixtures of these.
4. A method according to claim 1 in which the colloidal lubricating agent is selected from the group consisting of graphite, magnesium hydroxide and electrophoretically deposited silicon dioxide.
5. A method according to claim 1 in which the thickness of the layer does not exceed the average depth of irregularity which makes up the roughness in the ceramic coating.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH389174A CH574286A5 (en) | 1974-03-20 | 1974-03-20 | Refractory coating for continuous casting mould moving bands - comprises layers of refractory covered with resin filled with fine inorg matl |
| CH119375A CH585598A5 (en) | 1975-01-31 | 1975-01-31 | Refractory coating for continuous casting mould moving bands - comprises layers of refractory covered with resin filled with fine inorg matl |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1071944A true CA1071944A (en) | 1980-02-19 |
Family
ID=25686949
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA222,547A Expired CA1071944A (en) | 1974-03-20 | 1975-03-19 | Sealing layer for protective ceramic coatings on strip moulds of continuous strip casting machines |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1071944A (en) |
-
1975
- 1975-03-19 CA CA222,547A patent/CA1071944A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |